Practice Essentials

Renal trauma may manifest in a dramatic fashion for both the patient and the clinician. The incidence of renal trauma somewhat depends on the patient population being considered. Renal trauma accounts for approximately 3% of all trauma admissions and as many as 10% of patients who sustain abdominal trauma. In addition, renal trauma may occur in settings other than those thought of as a classic trauma setting. At most trauma centers, blunt trauma is more common than penetrating trauma, thereby making blunt renal injuries as much as 9 times more common than penetrating injuries. Both kidneys are at equal disposition for injury.[1]

The approach to renal injuries has changed over time, requiring diligent attention to recent literature. Namely, the tolerance for nonoperative or expectant management has increased, even in the most seriously injured kidneys, replacing the past tendency toward aggressive renorrhaphy.

Problem

Most renal trauma occurs as a result of blunt trauma. Renal injuries may be generally divided into 3 groups: laceration, contusion, and vascular injury. All subsets of renal trauma require a high index of clinical awareness and prompt evaluation and management.

Epidemiology

Frequency

The frequency of renal injury somewhat depends on the patient population being considered. Renal trauma accounts for approximately 3% of all trauma admissions and as many as 10% of patients who sustain abdominal trauma.

Using the National Trauma Data Bank, Grimsby et al reviewed data on 2213 pediatric renal injuries to determine injury mechanism and grade, demographics, treatment, and treatment setting. Most renal trauma in children was found to be low grade (79%) and blunt (>90%). Mean age at injury was 13.7 years, with 94% of patients being 5 to 18 years old. Only 12% of patients were admitted to a pediatric hospital. Although most children were treated conservatively at adult hospitals, the rate of nephrectomy was three times higher than for those patients treated at pediatric hospitals.[2]

Similarly, a review of 20 years of a prospectively maintained trauma database found that 70.6% of pediatric renal injuries from blunt trauma were low grade. Nephrectomy was required in only 1.4% of the 228 cases, and endoscopic interventions or percutaneous drainage procedures were needed in 2.4%.[3]

Presentation

The diagnosis of renal injury begins with a high index of clinical awareness. The mechanism of injury provides the framework for the clinical assessment. Particular attention should be paid to complaints of flank or abdominal pain. Urinalysis, both gross and, if necessary, microscopic, should be performed in patients who are thought to have renal trauma. Based on these initial measures, radiographic or operative investigation may follow.

Indications

Most blunt renal injuries are low-grade; therefore, they are usually amenable to treatment with observation and bed rest alone. Penetrating trauma is more likely to be associated with more severe renal injury, thus requiring a higher index of clinical awareness. Further, penetrating trauma is more often associated with other abdominal injuries requiring laparotomy, thus providing the opportunity for intraoperative renal staging and/or repair.

Patients with indications for emergent exploration include those with hemodynamic instability. Expanding hematomas or active hemorrhage suggests the possibility of high-grade renal injury. Patients with penetrating trauma who are stable and do not require urgent laparotomy for other possible intra-abdominal injuries may be observed without immediate renal exploration.

Unrelenting gross hematuria may require urgent exploration. However, the presence of a renal contusion does not typically require specific intervention. Findings from imaging studies may appear quite alarming, but most renal contusions resolve, particularly if the lesion appears to be of grade I-III.

Relevant Anatomy

In most instances, the kidneys are paired retroperitoneal structures. They lie against the psoas muscles. The superior aspect of the kidneys is somewhat protected by the lower ribs. However, the lower poles are inferior to the 12th ribs.

The parenchyma of the kidney has a segmental arterial supply. This anatomic arrangement becomes important in the management of renal lacerations. Blunt injuries tend to fracture along the planes between the segmental vessels, while penetrating injuries cross the segmental vessels.

Contraindications

For all practical purposes, no specific contraindications exist for surgical exploration of possible renal trauma. However, the general trend is toward a more selective approach. Current (2017) guidelines on urotrauma from the American Urological Association recommend noninvasive management strategies in hemodynamically stable patients with renal injury.[7]

Laboratory Studies

Urinalysis

Urinalysis provides rapidly available information in patients who may have a renal laceration; however, the data obtained must be viewed within a rational framework.

If gross hematuria is not present, a microscopic examination is advisable. Although in general, the degree of hematuria correlates with the likelihood of urinary tract trauma, renal injury with no hematuria has been reported. Reliance on urinalysis as the only modality to help diagnose renal trauma is fraught with difficulty. In fact, injuries such as renal artery laceration or avulsion may not generate any hematuria.

One study documents that 63% of patients with multisystem trauma had hematuria, of which 12.5% had a proven injury.[8] Other investigators have shown that as many as 11% of patients with renal gunshot wounds did not have hematuria.[9]

Thus, the presence or absence of hematuria should be viewed in the clinical context and not used as the sole decision point in the assessment of a patient with a possible renal laceration.

In children, 2-3 mL/kg of nonionic contrast is preferred.[11] For a satisfactory study, a systolic blood pressure above 90 mm Hg is needed. In order to save time, the contrast can be injected at the time of the initial resuscitation. Unstable patients who are emergently taken to the operating room, should be stabilized first and undergo one-shot IVU in the operating room once they are stabilized. The major limitation of intravenous pyelography (IVP) is that it can seldom, by itself, define the full extent of the injury.[12]

The purpose of the IVU is to determine the presence of two functioning renal units, the presence and extent of any urinary extravasation, and, in penetrating injuries, the likely course of the missile. Radiopaque markers (paper clips) taped to the skin at the bullet entrance and exit sites help predict the likelihood of the kidney being in the missile's path.

IVU is highly accurate for establishing the presence or absence of renal injury.[13] When it comes to staging parenchymal injury, however, IVU findings are usually nonspecific and not sensitive.[14, 15] Abnormal or equivocal IVU findings warrant further exploration or radiographic staging. For the hemodynamically stable patient, further and more accurate staging can be achieved with CT scanning.[16, 17] For unstable patients with abnormal IVU findings, surgical exploration is warranted.

Advantages of IVP are as follows:

Allows functional and anatomic assessment of both kidneys and ureters

Establishes the presence or absence of two functional kidneys

May be performed in the emergency department or operating room

Disadvantages of IVP are as follows:

Multiple images are required for maximal information, although a one-shot technique can be used

The radiation dose is relatively high (0.007-0.0548 Gy)

A full IVP usually requires a trip to the radiology suite

Findings do not reveal the full extent of injury (one investigation of penetrating trauma showed normal findings on six of 27 IVP examinations; all of those six patients had renal injuries)

Computed tomography

For stable patients, renal injury can be most accurately and completely imaged and staged using computed tomography (CT).[16, 17] CT imaging is both sensitive and specific for demonstrating parenchymal lacerations and urinary extravasations, delineating segmental parenchymal infarcts, and determining the size and location of the surrounding retroperitoneal hematoma and/or associated intra-abdominal injury (spleen, liver, pancreas, and bowel).

CT imaging has largely replaced the once standard IVU and arteriography. In the acute setting, CT scanning has completely replaced arteriography because it can also accurately delineate segmental and major arterial injuries. The present role of arteriography is with delayed renal bleeding or delayed arteriovenous fistula formation, for which super-selective arterial embolization is used.[18] Renal artery occlusion and global renal infarct are noted on CT scans by lack of parenchymal enhancement or a persistent cortical rim sign. Although reliable for demonstrating renal infarct, the disadvantage to using the rim sign is that it is usually not seen until at least 8 hours after injury.[19]

The advent of fast-scanning and image-reconstructing helical CT scanners has reduced turnaround times for abdominal trauma imaging to the 10-minute range. Seventy to 90 seconds before initiating helical CT scanning, 150-180 mL of intravenous contrast is given at 2-4 mL per second. Helical CT imaging is so quick (usually under 2 min) that only the arterial phase (20-30 seconds) and the early cortical phase (40-70 seconds) of the kidney are obtained. Arterial-phase imaging helps delineate any renal artery injury, while the early cortical phase still misses most parenchymal injuries.

Therefore, in order to complete the proper evaluation and staging of renal injuries, later imaging in the nephrogram phase (>80 seconds) is needed to detect renal parenchymal and venous injury, while delayed images (2-10 min) are often required to detect urine and blood extravasation. On delayed CT images, extravasated urine can be distinguished from blood in that it accumulates, while extravasated arterial contrast dilutes out after the bolus of contrast is stopped.[11, 20]

In children, four-phase CT with intravenous contrast (noncontrast, arterial, nephrographic, and pyelographic phases) is the choice for initial imaging. However, ultrasonography might also be used in children with minimal symptoms.[21]

Advantages of CT are that it (1) allows unsurpassed functional and anatomic assessment of the kidneys and urinary tract, (2) helps establish the presence or absence of 2 functional kidneys, and (3) allows for the diagnosis of concurrent injuries.

Disadvantages are that (1) it requires intravenous contrast in order to maximize information about functionality, hematoma, and, possibly, bleeding; (2) the patient must be stable enough to go to the scanner; and (3) full urinary assessment is dependent on the timing of contrast and scanning in order to view the bladder and ureters.

Angiography

With the advent of accurate and quick CT imaging, the uses for arteriography with renal trauma have diminished. Renal arteriography does provide the opportunity to stage the injury and, if necessary to embolize bleeding points at the same time.[13] However, in the acute setting, it is rarely used (renal arteriography and embolization for renal trauma) because it is time consuming and patients with active bleeding need to undergo immediate exploratory laparotomy. Furthermore, during laparotomy, the kidney can be explored and surgically reconstructed. Arteriography and superselective embolization continues to play an important role in the evaluation and treatment of symptomatic posttraumatic arteriovenous fistulas or persistent delayed renal bleeding.[18]

Advantages are that it (1) has the capacity to aid in both the diagnosis and treatment of renal injuries and (2) may further define injury in patients with moderate IVP abnormalities or with vascular injuries.

Disadvantages are as follows:

Invasive

Requires contrast

Requires mobilization of resources to perform the study, which may be time-consuming

Requires moving the patient to the radiology suite

Ultrasonography

Experience with the evaluation of suspected acute renal traumatic injury by ultrasonography has been primarily from Europe.[22] In well-trained and experienced hands, renal lacerations and hematomas can be reliably identified and delineated. Limitations of ultrasonography include an inability to distinguish fresh blood from extravasated urine and an inability to identify vascular pedicle injuries or segmental infarcts. Only with close color and pulsed Doppler interrogation can a vascular injury be diagnosed. Furthermore, concomitant rib fractures, bandages, intestinal ileus, open wounds, or morbid obesity severely limit renal visualization.

In general, the accuracy of ultrasonography for evaluating the retroperitoneum is variable, time consuming, and highly operator dependent. Therefore, the routine use of ultrasonography for screening acute renal trauma is not advocated.

However, ultrasonography has proven useful and reliable for evaluating blunt intra-abdominal injuries by detecting the presence of hemoperitoneum. In hemodynamically unstable patients, it is used as a less invasive replacement for diagnostic peritoneal lavage. In stable blunt trauma victims, ultrasonography is used to direct patients to CT imaging when hemoperitoneum is noted and to observation in those with negative findings

Diagnostic Procedures

Operative diagnosis

Depending on the mechanism of injury, many patients who sustain renal laceration have associated intra-abdominal injuries that require urgent exploration. The clinical situation may have precluded the opportunity to perform the aforementioned diagnostic modalities.

The surgeon should be prepared to make the diagnosis of renal injury intraoperatively. Lateral retroperitoneal hematomas may alert the surgeon to the presence of renal laceration. Direct evidence of penetrating trauma should also provide evidence of renal laceration. Other renal trauma, including renal pelvis or ureteral injuries, should be sought and identified.

Although the medical consensus is not complete, evidence exists that not all perirenal hematomas discovered at laparotomy require exploration. Theories range from simple observation to exploration with vascular control. The optimal course depends on the physician's experience and the institution's resources. Increasingly, even severe renal injuries are being safely managed nonoperatively.

Blunt trauma and gross hematuria

Gross hematuria is the most reliable indicator for serious urological injury. The degree of hematuria, however, does not correlate with the degree of injury. In fact, renal pedicle avulsion or acute thrombosis of segmental renal arteries can occur in the absence of hematuria, while renal contusions can present as gross hematuria.

Blunt trauma, microscopic hematuria, and shock

Significant microscopic hematuria is greater than five red blood cells per high-power field (RBC/HPF) in the first voided or catheterized specimen. Shock is any presence of systolic blood pressure less than 90 mm Hg during transport or upon arrival in the emergency department. Blunt trauma patients with microhematuria and no shock have minor renal injuries in nearly all cases.

Miller and McAninch, based on findings in more than 2000 blunt renal trauma injuries, determined that a grade 2 or more severe renal injury will be missed in less than 0.2% of cases.[1] These patients are the victims of multiple trauma, and, thus, during the evaluation of other intra-abdominal injuries, most of the missed major renal injuries are be detected. When patients who were imaged for associated intra-abdominal injuries are included, only 0.03% of significant renal injuries were not identified.

Major deceleration injury

The kidney primarily floats free in a bed of fat contained within the envelope of the Gerota fascia. The kidney is fixed at only two points, the ureter and the vascular pedicle. Because of poor fixation, the kidney can be easily dislocated by sudden acceleration or deceleration.

Kidney dislocation can result in tearing of the collecting system at the ureteropelvic junction (UPJ) or tearing of renal artery intima, resulting in partial-to-complete vessel occlusion. Such injuries can occur with major deceleration, as in head-on motor vehicle accidents (MVA) or falls from great heights, or from marked flexion extension, as with pedestrian versus motor vehicle collisions. Pediatric patients are particularly prone to this mechanism of injury. In general, all rapid deceleration injuries warrant renal imaging, even in the absence of hematuria.[10, 24]

In comparison to adults, children’s kidneys are relatively much larger for their body size. The kidneys are also not as well protected with perirenal fat, which is usually scant, and lower ribs that are incompletely ossified. Therefore, children are particularly prone to injury. However, the majority of blunt renal injuries are contusions that require no active therapy. Hypotension is often an unreliable predictor of significant renal injury, as children can maintain a normal blood pressure despite extensive blood loss.[25]

Traditionally, all children with any degree of microscopic hematuria after blunt trauma have undergone renal imaging. In a meta-analysis of all reported series of children with hematuria and suspected renal injury,[26] Morey et al noted that only 2% (11 of 548) of patients with insignificant microscopic hematuria (< 50 RBC/HPF) had a significant renal injury. Furthermore, these 11 patients all had other significant injuries that required abdominal and, thus, renal imaging. They concluded that renal injury is suggested in children in stable condition with gross or significant microscopic hematuria (>50 RBC/HPF) or with moderate-to-severe multisystem trauma (regardless of the hematuria degree), and these children should undergo renal imaging.

Patients who do not initially undergo renal imaging who have persistent or worsening hematuria should also be imaged. Although renal pedicle injuries can occur without hematuria, they are likely to be associated with severe multisystem trauma that requires abdominal imaging anyway. For suspected renal injury, CT scanning is the best study for staging a solid organ injury.

Associated injuries suggesting underlying renal injury

These include blunt trauma and a flank ecchymosis, lumbar vertebral or transverse process fractures, lower rib (11th or 12th) fractures, and severe mechanism of injury. Another indication for imaging is a penetrating flank or abdominal injury with which the entrance and exit sites (or radio-opaque density) are in the path of the kidney, regardless of the degree of hematuria.

Also see the Medscape Reference article Imaging in Kidney Trauma and the flow chart in the image below.

Injury scaling

To determine the appropriate management for a renal injury, the renal injury first needs to be accurately staged. The American Association for the Surgery of Trauma (AAST) has defined renal trauma in five grades, as follows[27, 28] :

Grade 4 - Renal cortical laceration extending into the collecting system (as noted by contrast extravasation), or a segmental renal artery or vein injury (noted by a segmental parenchymal infarct), or main renal artery or vein injury with a contained hematoma

Grade 5 - Shattered kidney, avulsion of the renal pedicle, or thrombosis of the main renal artery

Nonoperative Treatment

In the setting of blunt renal trauma and selected instances of penetrating renal trauma, a nonoperative approach may be selected. Patient selection is the preliminary step in adopting a nonoperative management strategy to renal trauma. One series, with predominantly blunt mechanisms of injury, documented that 85% of patients were treated successfully without surgery. Ultimately, the exclusion of concurrent injury may be the key point in treating patients nonoperatively.

The anatomic structure of the kidney lends itself to nonoperative management in the setting of blunt trauma. The kidney has an end artery blood supply with a segmental pattern of division that supplies the renal parenchyma. When subjected to blunt force that causes a laceration, the laceration tends to occur through the parenchyma. The resulting hematoma may displace renal tissue, but the segmental vessels themselves often are not lacerated.

The closed retroperitoneal space around the kidney also promotes tamponade of bleeding renal injuries. Finally, the kidney is rich in tissue factor, the molecule that activates the extrinsic coagulation cascade, further promoting hemostasis after injury.

Interventional radiology has extended the ability to treat renal lacerations nonoperatively. Techniques have included the following:

Percutaneous drainage of perinephric fluid collections or urinomas

Endourologic stenting

Angiography with selective embolization

For example, Wang et al reported that emergency transcatheter arterial embolization produced complete hemostasis in 80 of 83 patients with acute renal hemorrhage. Renal artery computed tomography angiography (CTA) was used to localize the bleeding artery in 35 of their cases. Embolic agents used varied with arteriographi presentation and included gelatin sponge, polyvinyl alcohol particles, and coils.[30]

In children with grade IV renal injury who are receiving conservative treatment, Lee et al recommend performing a follow-up imaging study 4-5 days after the trauma when any of the following are present[31] :

Need for transfusion

Main laceration location in the antero-medial portion of the kidney

Intravascular contrast extravasation

Large perinephric hematoma (>2.2 cm)

In their study of 26 consecutive cases of grade IV renal trauma in children, more patients with those predictive factors required urologic intervention, typically 4-8 days after the trauma.[31]

Operative Treatment

The goals of operative therapy for renal laceration incorporate the two basic principles of hemorrhage control and renal tissue preservation, which must be balanced for each individual patient. Attempts to find a universal plan for this approach have generated controversy in the medical literature. The mindset of the medical community has also been changing as established practice patterns have been examined, challenged, and reassessed.

An additional benefit of operative therapy is the ability to address concurrent injuries. One study documented that 80% of patients with renal laceration had other associated injuries. In that same study, 47% of the patients with renal laceration had an associated injury that required immediate laparotomy.

Indications for renal exploration

In order to select a renal injury for nonoperative management, the injury needs to be imaged and accurately staged. An incompletely staged renal injury requires surgical exploration. Not all penetrating renal injuries require surgical exploration. The use of the improved imaging technique of CT has largely been responsible for the decreased rate of renal explorations at the authors’ institution. Guidelines for the surgical exploration of the injured kidney vary.

The only absolute indication for surgical renal exploration is a patient with external trauma and persistent renal bleeding. Signs of continued renal bleeding are a pulsatile, expanding, or uncontained retroperitoneal hematoma. Another sign is avulsion of the main renal artery or vein as noted by CT or arteriography.

Relative indications include nonviable tissue. Substantial devitalized renal parenchyma (>25%) is a relative indication for exploration.[32] Husmann and Morris[33] noted that injuries with significant nonviable renal tissue (25-50%) associated with parenchymal laceration that are managed nonoperatively have a high complication rate (82%).

Husmann et al further compared the results of the nonoperative and surgical management of major renal lacerations and devitalized renal fragments after blunt trauma. Their findings demonstrated that when such renal injuries are associated with an intraperitoneal organ injury, the postinjury complication rate is much higher unless the kidney is surgically explored and repaired. By surgically repairing such injuries, they reduced the overall morbidity from 85% to 23%. Concomitant pancreatic and bowel injuries were particularly associated with higher rates of infected urinomas and abscesses.

Furthermore, since nearly all blunt trauma patients with intraperitoneal organ injuries undergo celiotomy by the general surgeon, this offers the opportunity to explore and repair the kidney with such major parenchymal injuries.

A systematic review by Chiron et al identified three risk factors that are not included in the grade 4 renal injury classification, but are associated with hemodynamic instability and need for surgery, as follows[32] :

Perirenal hematoma >3.5 cm

Intravascular contrast extravasation

Medial renal laceration

Additional relative indications include the following:

A major devitalized segment

Injury associated with urinary extravasation

Extensive renal injury

A large retroperitoneal hematoma, even without intraperitoneal injury

Urinary extravasation

Urinary extravasation in itself does not demand surgical exploration. Extravasation confirms the diagnosis of a major renal injury. Persistent extravasation or signs of sepsis usually require intervention. In general, urinary extravasation resolves spontaneously in the majority of patients with blunt trauma. In select patients, expectant management does not reduce the renal salvage rate and does not prolong hospitalization.

Nonoperative therapy may also require delayed intervention. However, the usual complications of urinoma and persistent urinary leak can be successfully managed by either percutaneous or endoscopic techniques, thus avoiding celiotomy and renal exploration. Matthews et al[34] reported that in patients with major renal injury and urinary extravasation who are managed conservatively, urinary extravasation spontaneously resolved in 87%. Extravasation persisted in 13% and was successfully managed endoscopically (eg double-J stent). Overall hospitalization lasted 8 days and was not prolonged by the need for delayed intervention.

Ureteropelvic junction (UPJ) injuries rarely heal spontaneously and thus are often best managed by surgical repair at the time of injury. Conservative management of such injuries is fraught with persistent urine leakage, urinoma formation, ileus, and infection.

Incomplete staging

Only complete definition of the renal injury by appropriate imaging studies permits the selection of nonoperative management. Incomplete staging demands either further imaging or renal exploration and reconstruction. In the unstable patient who requires emergent celiotomy, the kidney can only be imaged by one-shot IVU on the operating room table. The nephrogram of the injured kidney is often poorly opacified due to the injury and is worsened by any hemodynamic instability. In so doing, the full extent of the injury is indeterminate. In such circumstances, the kidney should be explored after obtaining proximal vascular control.

The unexpected finding of a retroperitoneal hematoma upon celiotomy should be evaluated by on-table, one-shot IVU. If IVU results are abnormal or indeterminate or if the kidney is persistently bleeding, then the kidney should be explored.

Arterial thrombosis

Major deceleration injuries can result in stretching on the renal artery and tearing of the vessel intima, resulting in thrombosis of the main renal artery or its segmental branches and thus causing infarction of the renal parenchyma. Prompt diagnosis and the time until operation of a unilateral complete arterial thrombosis is vital to salvaging the kidney. The chance of renal salvage is remote after 12 hours of ischemia.

If the contralateral kidney is healthy, there is some controversy as to whether to attempt revascularization or to observe. If renal ischemia exceeds 12 hours, the kidney should be allowed to slowly atrophy. Nephrectomy should be performed only if delayed celiotomy is being performed for an associated injury or if persistent hypertension develops postoperatively. Bilateral complete renal artery thrombosis or a solitary kidney demands more immediate exploration and revascularization.

Penetrating trauma

The only absolute indication for exploration is persistent renal bleeding. Nearly all penetrating renal injuries should be managed surgically. The exception is stable patients with no missile penetration of the peritoneum in whom the injury is well staged by computed tomography.

Wessels et al have shown that gunshot wound victims who have no intra-abdominal organ injury and a demonstrated grade 1-2 renal injury, when managed conservatively, are relatively complication free. In sharp contrast, one of four expectantly managed grade 3-4 injuries were complicated by delayed renal bleeding.[35]

A study by Bjurlin et al found that selective nonoperative management of penetrating renal injuries resulted in a lower mortality rate, a decreased incidence of blood transfusion, and a shortened mean ICU and hospital stay compared with nephrectomy; however, results were similar to renorrhaphy. Rates of complication were low with selective nonoperative management and were comparable to operative management.[36]

Stab wounds posterior to the posterior axillary line are less likely to have an associated visceral injury. When the diagnostic peritoneal lavage or CT scan is negative for intraperitoneal organ injury and the renal injury not severe, observation of the renal injury may be appropriate. Most abdominal penetrating injuries undergo celiotomy by the general surgeons. The presence of an unexpected retroperitoneal hematoma upon exploratory laparotomy when the renal injury has not been fully staged radiographically usually warrants renal exploration.

Some controversy remains with the use of postoperative drains in the setting of renal trauma. The general trend has been away from the routine use of drains in this setting, although some centers still advocate their use. Suction drains should be avoided after renal repair.

Preoperative Details

Patients with renal injuries should be managed with initial attention to the basic ABCDEs outlined in Advanced Trauma Life Support protocols. Because many patients have multisystem trauma with concurrent injuries, a systematic approach to the initial assessment and resuscitation allows for identification of other injuries. The decision-making process becomes more involved as additional injuries are found. For additional details, see Critical Care Considerations in Trauma or Initial Evaluation of the Trauma Patient.

Intraoperative Details

Techniques for renal exploration and repair

Primary vascular control is achieved prior to all renal explorations by routinely obtaining proximal vascular control. For vascular control, the ipsilateral renal artery and vein are isolated individually with vessel loops.

The kidney is then exposed by incising the Gerota fascia lateral to the colon. When brisk bleeding is encountered, the renal artery is temporarily occluded with Rummel tourniquets. Warm ischemic time should not greatly exceed 30 minutes, in order to avoid permanent renal ischemic damage. If bleeding persists, the renal vein is occluded by Rummel tourniquet placement, in order to eliminate back bleeding. Temporary occlusion of the renal artery is needed in patients with renal vascular injuries, those in shock, and those with large or expanding retroperitoneal hematomas.

Rostas et al have proposed that exploration of the Gerota fascia may be used selectively rather than routinely for patients with renal gunshot wounds. Their retrospective 10-year review of 63 patients with renal gunshot wounds who underwent exploratory laparotomy concluded that most such patients do not require exploration of the Gerota fascia. Compared with patients (n=28) who underwent exploration of the Gerota fascia, those who did not (n=35) experienced significantly lower mortality (14% versus 29%), had very low complication rates, and were unlikely to need surgical intervention due to renal-associated complications.[37]

Renal reconstruction

In the absence of persistent hemodynamic instability or coagulopathy, renal reconstruction is safe and effective. The method of kidney reconstruction is dictated by the degree and location of the injury, and not by the associated intra-abdominal injuries. In the face of concomitant major pancreatic or colonic injuries with frank fecal contamination, renal reconstruction is successful, with only a slightly increased complication rate. The reconstructive principles for renal injures are as follows:

Adequate and broad exposure of the kidney and injured area

Temporary vascular occlusion for brisk renal bleeding not well controlled by manual compression of the parenchyma

Sharp excision of all nonviable parenchyma

Meticulous hemostasis (particularly, arterial)

Watertight closure of the collecting system

Parenchymal defect closure by approximation of the capsular/parenchymal edges over a Gel-foam bolster or coverage with omentum, perinephric fat, peritoneum, or polyglycolic acid mesh

Interposition of an omental pedicle flap between any vascular, colonic, or pancreatic injury and the injured kidney

Ureteral stent placement for a renal pelvis or ureteral injury

Retroperitoneal drain placement: The authors prefer to use a Penrose drain. Unless drainage is excessive, the Penrose drain is removed after 48 hours. Additionally, the urinary tract injury and the pancreatic injury are always drained separately.

Indications for nephrectomy

When proximal vascular control is initially achieved, before all renal explorations, nephrectomy is required in less than 12% of cases.[38] When primary vascular control is not achieved and massive bleeding is encountered, in the rush to control bleeding, a kidney that could have been salvaged may be unnecessarily sacrificed. Overall, nephrectomy is required when the patient is persistently hemodynamically unstable and, thus, is a life-saving maneuver. Other indications for nephrectomy are as follows:

Grade 5 injuries that are deemed irreparable(eg, major vascular pedicle injury, particularly on the right side)

Postoperative Details

As with all trauma patients, the postoperative course should be monitored to ensure successful hemostasis. Serial hematocrit measurements should be considered. In patients in whom a damaged but perfused kidney is left in situ, renovascular hypertension remains a theoretical possibility and the patient should be monitored clinically for this entity.

Follow-up

Complications

Complications that can follow renal trauma are dependent on the grade of the initial renal injury and the method of management.[39] In most cases, resulting complications are usually of minimal long-term morbidity, can be successfully managed by endourologic and percutaneous techniques, and do not significantly prolong the mean days of hospitalization.[40, 41]

Early complications

Early complications, those that occur within 1 month of injury, are urinoma, delayed bleeding, urinary fistula, abscess, and hypertension. Prolonged urinary extravasation is the most common complication after renal trauma.[4, 40]

Urinomas occur in less than 1% of renal trauma cases. Small, uninfected, and stable collections do not require intervention. Larger collections are usually successfully managed by the endoscopic or percutaneous placement of a ureteral/nephrostomy tube.

Delayed renal bleeding most commonly occurs within 2 weeks of injury. When bleeding is heavy or symptomatic, transfusions, angiography, and superselective embolization[18] may be required.

Urinary fistulas can occur in association with an undrained collection or from large segments of devitalized renal parenchyma.

Abscesses of the retroperitoneum are associated with ileus, high fever, and sepsis. Most collections can be easily drained percutaneously. The extent of the abscess and the presence of loculations are well delineated by CT imaging.

Hypertension in the early postoperative period is usually renin mediated and transient, and it does not require any treatment.

Late complications

Scarring in the region of the renal pelvis and ureter after renal trauma can result in urinary obstruction and, subsequently, lead to stone formation and chronic infections.

Arteriovenous fistula more commonly occurs after a renal stab wound and can present with delayed bleeding.[18] Angiography can help determine the size and location of the fistula. In most cases, vessel embolization can be used to successfully close the fistula.

Long-term hypertension from renal trauma is a rare complication that is overdiagnosed. The experience at San Francisco General Hospital is that sustained hypertension occurs in only 0.2% of cases.[1] The etiology for hypertension after renal injury is renal ischemia stimulating the renin-angiotensin axis. Long-term follow-up of renal trauma patients is important in order to not miss these late complications, which are often of insidious onset and silent progression.

Outcome and Prognosis

In many cases of renal trauma, the outcome and prognosis depend on the associated injuries. In situations in which nonoperative management is used, concern exists about leaving perfused but nonviable renal tissue in situ, which may lead to hypertension. However, the occurrence of hypertension in this setting seems to be rare. One study documents no evidence of hypertension after 5 years of follow-up in children who had sustained renal trauma. Other series report only isolated instances of hypertension. Therefore, the risk of hypertension alone does not seem to warrant surgical exploration in cases with nonperfused renal segments.

Future and Controversies

Preoperative IVP for penetrating trauma

Proponents of the one-shot IVP point out that it can be performed as the patient is being prepared for surgery and that it allows a quick assessment of the functionality of the contralateral kidney.

Opponents believe that preservation of renal tissue is always a goal as long as the approach is safe for the patient. Knowledge of the functional status of the contralateral kidney does not change whether or not trying to salvage the kidney is safe. The timing of the injection may yield suboptimal views, and often, more time is needed to obtain images than is anticipated.

The consensus on this technique remains incomplete. Intraoperative IVP can potentially allow leaving a perinephric hematoma unexplored if the study shows findings of a completely normal system. Some practitioners make extra efforts to succeed with operative salvage of a damaged kidney if the contralateral kidney is known to be absent.

Operative technique (central vascular control)

Proponents believe that data demonstrate enhanced renal salvage when vascular control is obtained outside the Gerota fascia. This technique allows controlled assessment of the nature of the renal laceration, and it may impart less trauma on the vessels compared to more urgent control measures.

Opponents believe that not all renal injuries have sufficient bleeding to warrant central control of vessels. The technique requires some operative time and exposes the renal vessels to potential operative trauma. Anatomic variants, such as multiple arteries or veins, may not be recognized and may elicit a false sense of security.

Hypertension

Although concern exists that leaving perfused but nonviable renal tissue in situ potentially leads to hypertension, the occurrence of hypertension in this setting seems to be rare. One study documents no evidence of hypertension after 5 years of follow-up in children who had sustained renal trauma. Other series report only isolated instances of hypertension. Therefore, the risk of hypertension alone does not seem to warrant surgical exploration in cases with nonperfused renal segments.

Nonperfused kidney

Controversy exists regarding whether to revascularize a nonperfused kidney. The incidence rate of renal salvage in the setting of a nonperfused kidney due to trauma has been reported to be approximately 0%. Isolated case reports of success do exist. Most centers advocate an expectant management approach.

The need for ultimate nephrectomy also remains somewhat controversial. Possible or documented renovascular injury continues to be a controversial arena of renal injury management. Only aggressive intervention provides the opportunity for renal salvage. However, the clinician must be aware that the salvage rate is low, and, ultimately, the life of the patient must take priority over the life of the kidney. Continued investigation and evolution of surgical techniques may help resolve this controversy.

Conclusion

The approach to the diagnosis and management of renal trauma continues to evolve. In the setting of significant hemodynamic instability, operative exploration remains the diagnostic and therapeutic modality of choice. In patients with blunt trauma and in certain cases of penetrating trauma, a progressive trend is towards nonoperative management of renal trauma.

Continued change in the approach to renal trauma is almost a certainty. Interventional radiology and endourologic manipulation have increased the ability to successfully treat patients without surgery and to address common complications of renal trauma. Numerous diagnostic options exist in the setting of a stable patient. With awareness of these modalities, the clinician can provide each patient with optimal treatment.

Urinary drainage should be performed in patients with complications such as enlarging urinoma, fever, increasing pain, ileus, fistula or infection (Recommendation; evidence strength: Grade C); ureteral stenting should be used for drainage and may be augmented by percutaneous urinoma drain, percutaneous nephrostomy, or both. (Expert Opinion)

Additional Contributors

Acknowledgements

The authors and editors of Medscape Reference gratefully acknowledge the contributions of previous authors Douglas M Geehan, MD, and Richard A Santucci, MD, FACS,to the development and writing of this article.